This application relates to systems and methods for link state database exchanges and processes when two Open Shortest Path First (OSPF) routers are forming a full adjacency. More particularly, the present invention relates to systems and methods for eliminating unnecessary link state database exchanges and processes.
Link state databases are exchanged when two Open Shortest Path First (OSPF) routers are trying to establish a full adjacency. If the full adjacency is to be formed between the OSPF routers, the link state databases are synchronized through a database exchange procedure. A first router sends a second router a summary of a link state database of the first router through a set of Database Description (DD) packets that contain a header of every Link State Advertisement (LSA) in the link state database of the first router. For every received LSA header that is contained in the DD packets, the second router compares the LSA header with a corresponding LSA instance in a link state database of the second router. The second router sends the first router a request for the LSA if the LSA instance in the database of the second router is older. The second router sends the first router a summary of a link state database of the second router through a set of Database Description (DD) packets that contain a header of every Link State Advertisement (LSA) in the link state database of the second router. For every received LSA header that is contained in the DD packets, the first router compares the LSA header with a corresponding LSA instance in the link state database of the first router. The first router sends the second router a request for the LSA if the LSA instance in the database of the first router is older.
An adjacency becomes full from the point of view of the first router, when the first router finishes sending the summary of the link state database of the first router and processing all the DD packets from the second router and gets all the LSAs from the second router that the first router has requested. An adjacency becomes full from the point of view of the second point of view, when the second router finishes sending the summary of the link state database of the second router and processing all the DD packets from the first router and gets all the LSAs from the first router that the second router has requested. A full adjacency between the first router and the second router is formed successfully when an adjacency becomes full from the point of view of both the first router and the second router.
For a large database, eliminating the unnecessary database exchanges may speed up establishment of full adjacency and save lots of link bandwidths for transmission of the unnecessary DD packets and central processing unit (CPU) cycles for the process of the packets.
Conventional mechanisms and methods use a passive approach for eliminating unnecessary link state database exchanges and processes. For two routers to establish a full adjacency, if a first router receives the same or a more recent instance of a LSA listed in a DD packet from a second router, the first router does not need to list the LSA in the DD packet to be sent to the second router. There are some concerns regarding this passive approach. For example, about 50% of the unnecessary exchanges and processes of the link state database are done in the passive approach. Such unnecessary exchanges of link state databases can consume link bandwidth between routers.
From the foregoing, systems, devices, and methods for eliminating undesired link state database exchanges and processes are desired.